1. Field of Invention
The present invention relates to a domain gateway control system and its method. More particularly, the invention relates to a domain gateway control system and its method in which a gateway device is used as a packet format conversion device between a domain and an Ethernet to make net devices in the domain form a network group dedicated to the domain.
2. Related Art
In the prior art, upon acquiring a data packet transported over a network, an L2 (data link layer) net device compares a destination Media Access Control (MAC) address data of the data packet with a device MAC table data built in the net device, and searches in the device MAC table data for port number data of a communication port corresponding to the destination MAC address data to output the data packet through the corresponding communication port. However, when no port number data of communication port corresponding to the destination MAC address data exists in the device MAC table data, the net device broadcasts the data packet from all communication ports of the net device except the communication port acquiring the data packet.
Meanwhile, the net device also compares a source MAC address data of the data packet packet with the device MAC table data. If the source MAC address data does not exist in the device MAC table data, the source MAC address data and port number data of the communication port acquiring the data packet are recorded in the device MAC table data. On the contrary, when the source MAC address data exists in the device MAC table data, the net device compares the source MAC address data and port number data of the communication port acquiring the data packet with data recorded in the device MAC table data. If the source MAC address data and the port number data of communication port are the same as the data recorded in the device MAC table data, the data in the device MAC table data remains unchanged. If the port number data of communication port which corresponds to the source MAC address data is different from the data recorded in the device MAC table data, depending on the demands of the designer, the source MAC address data and the corresponding port number data of communication port will either be updated in the device MAC table data or the port number data of communication port corresponding to the source MAC address data will be added in the device MAC table data.
For example, FIG. 1 is a schematic view of connection of net devices in the prior art. Connection architecture of an L2-net device-switch with other net devices is provided for illustration. In FIG. 1, a switch 1 is connected to a net device B and a net device C. When a remote net device A needs to communicate with net device B, data packets are transmitted between net device A and net device B through the network, and the switch 1 records source MAC address data of the data packets and port number data of a communication port receiving the data packets respectively.
It is assumed that the switch 1 acquires, through a No. I communication port 11, a data packet P1 transmitted by the net device A. The source MAC address data of the data packet P1 is the MAC of the net device A, and the destination MAC address data of the data packet P1 is the MAC address of the net device B. The switch 1 compares the source MAC address data of the data packet P1 with a device MAC table data. If the MAC address of net device B is stored in the device MAC table data and the MAC address of net device B corresponds to the No. II communication port 12 of the switch 1, the switch 1 outputs the data packet P1 through the No. II communication port 12 to transport the data packet P1 to net device B. On the contrary, if the MAC address of net device B is not stored in the MAC table data, the switch 1 broadcasts the data packet P1 through all communication ports except the No. I communication port 11.
If the switch 1 determines the MAC address of net device A, it will record the MAC address of net device A and the No. I communication port 11 corresponding to the MAC address of net device A in the MAC table data.
Next, it is assumed that the switch 1 acquires, through the No. II communication port 12, a data packet P2 transmitted by net device B. The source MAC address data of the data packet P2 is the MAC address of the net device B, and the destination MAC address data of the data packet P2 is the MAC address of the net device A. If the switch 1 determines that the MAC address of net device B is not in the system, the MAC address of the net device B will be recorded in the MAC table data by the switch 1. However, if the switch 1 determines that the MAC address of the net device A is already learnt and knows that the MAC address of the net device A corresponds to the No. I communication port 11, the switch will output the data packet P2 output from the net device B through the No. I communication port 11.
Next, it is assumed that the switch 1 acquires a data packet P3 of the net device C through a No. III communication port 13 and the data packet P3 points to the net device B or the net device A. When the switch 1 first learns a MAC address of the net device C from the data packet P3, it will to update the MAC table data. Subsequently, the switch 1 outputs the data packet P3 heading for net device A directly through the No. I communication port 11, or uses the No. II communication port 12 to output the data packet P3 heading for net device B.
If only the L2-net protocol is applied, the other net devices can also perform operations that include a learning operation of a source MAC address data of a data packet and a forwarding operation of the data packet. As the number of net devices increases gradually and the network scale gets larger gradually, each net device needs to learn and record an increased number of MAC addresses. The net devices must have storage units having a larger memory capacity to record MAC addresses of other net devices. In addition, even if each net device has a built-in MAC update and stripping mechanism to perform better update and processing on data in the MAC table data, the demands for the memory capacity of the storage unit cannot be effectively restrained. Additionally, once data stored in the storage unit reaches an upper limit of the memory capacity, even if the MAC update and stripping mechanism are used, a processor of the net device cannot be prevented from continuously performing a MAC learning operation, and, as a result, extra software or hardware resources must be provided for the processor to assist the MAC learning operation, resulting in unnecessary resource consumption. Furthermore, with the demands for increasing memory capacity, the manufacturing costs of the storage units and net devices in which the storage units are applied increase accordingly.
Therefore, the problem that manufacturers encounter is how to use net devices with limited memory capacity in net architectures of different scales.